54,775 research outputs found
Magnetic susceptibility anisotropies in a two-dimensional quantum Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions
The magnetic and thermodynamic properties of the two-dimensional quantum
Heisenberg antiferromagnet that incorporates both a Dzyaloshinskii-Moriya and
pseudo-dipolar interactions are studied within the framework of a generalized
nonlinear sigma model (NLSM). We calculate the static uniform susceptibility
and sublattice magnetization as a function of temperature and we show that: i)
the magnetic-response is anisotropic and differs qualitatively from the
expected behavior of a conventional easy-axis QHAF; ii) the Neel second-order
phase transition becomes a crossover, for a magnetic field B perpendicular to
the CuO(2) layers. We provide a simple and clear explanation for all the
recently reported unusual magnetic anisotropies in the low-field susceptibility
of La(2)CuO(4), L. N. Lavrov et al., Phys. Rev. Lett. 87, 017007 (2001), and we
demonstrate explicitly why La(2)CuO(4) can not be classified as an ordinary
easy-axis antiferromagnet.Comment: 6 pages, 3 figures, Revtex4, accepted for publication in Phys. Rev.
Spin-1 Particles with Light-Front Approach
For the vector sector, i.e, mesons with spin-1, the electromagnetic form
factors and anothers observables are calculated with the light-front approach.
However, the light-front quantum field theory have some problems, for example,
the rotational symmetry breaking. We solve that problem added the zero modes
contribuition to the matrix elements of the electromagnetic current, besides
the valence contribuition. We found that among the four independent matrix
elements of the plus component in the light-front helicity basis only the one carries zero mode contributions.Comment: 5 pages. 3 Figures, use latex and EPJ styl
Development of 15 nuclear microsatellite markers in Deuterocohnia (Pitcairnioideae; Bromeliaceae) using 454 pyrosequencing
Resgate e conservação da flora no aproveitamento hidrelétrico Cana Brava, Goiás: relatório final.
Introdução e objetivos; CaracterÃsticas gerais do reservatório; Estratégias de ação e métodos; Resultados; Anexo 1 "Check list" do Aproveitamento Hidrelétrico Cana Brava, Goiás, Brasil. Anexo 2 Lista de especies com germoplasma resgatado na área de influência do AHE Cana Brava.bitstream/item/130278/1/Rel-Final-Nov-2002.pd
Germinação de sementes de melancia sob diferentes métodos de tratamento com reguladores vegetais.
A melancia é uma cultura importante para o Brasil pela demanda intensiva de mão-de-obra rural, perfil predominante pela produção familiar e retorno em torno de 85 dias em relação à s outras oleráceas. O uso de reguladores de crescimento pode favorecer o desempenho das plântulas, acelerando a velocidade de emergência de sementes de várias espécies. Acredita-se que possam desempenhar um papel importante na regulação de certos aspectos das sementes, além de estarem envolvidas no crescimento de frutos e outros determinados fenômenos fisiológicos. Sementes de melancia cv. Crimson Sweet foram submetidas a dois métodos de tratamento com regulador: a) sementes embebidas: embebição das sementes em regulador por 8 horas; b) substrato embebido em regulador sendo utilizados os reguladores: ácido salicÃlico (0; 0,5; 5; 25 e 50 ?mol.L-1); putrescina (0; 50; 100; 500 e 1000 ?mol.L-1) e ácido giberélico (0, 50, 100 e 500 ?g.g-1). Para ácido salicÃlico e putrescina utilizou-se o delineamento experimental inteiramente casualizado em esquema fatorial 2 x 5 (métodos de tratamento x concentrações do regulador), com ácido giberélico foi utilizado esquema fatorial 2 x 4, com quatro repetições de 50 sementes cada. O método mais eficiente com ácido salicÃlico foi o uso de substrato embebido, juntamente com 0, 25 e 50 ?mol.L-1.A concentração de 1000 ?mol.L-1 de putrescina teve efeito negativo sobre as raÃzes das plântulas.50 e 100 ?g.g-1deGA3 promoveu maior desenvolvimento da parte aérea das plântulas.500 ?g.g-1 de GA3 teve efeito fitotóxico sobre as sementes e posteriormente sobre as plântulas de melancia
Investigation of the agricultural resources in Sri Lanka
The author has identified the following significant results. Several in-house capabilities were developed. The facilities to prepare color composites of excellent quality were developed, using bulk B/W 70 mm transparencies or 1:1,000,000 positive transparencies. These color composites were studied through optical devices on light tables. A zoom transfer scope was also added, enabling direct transfer of LANDSAT composite data on to base maps
Absolute quantification of the host-to-parasite DNA ratio in Theileria parva-infected lymphocyte cell lines
Theileria parva is a tick-transmitted intracellular apicomplexan pathogen of cattle in sub-Saharan Africa that causes East Coast fever (ECF). ECF is an acute fatal disease that kills over one million cattle annually, imposing a tremendous burden on African small-holder cattle farmers. The pathology and level of T. parva infections in its wildlife host, African buffalo (Syncerus caffer), and in cattle are distinct. We have developed an absolute quantification method based on quantitative PCR (qPCR) in which recombinant plasmids containing single copy genes specific to the parasite (apical membrane antigen 1 gene, ama1) or the host (hypoxanthine phosphoribosyltransferase 1, hprt1) are used as the quantification reference standards. Our study shows that T. parva and bovine cells are present in similar numbers in T. parva-infected lymphocyte cell lines and that consequently, due to its much smaller genome size, T. parva DNA comprises between 0.9% and 3% of the total DNA samples extracted from these lines. This absolute quantification assay of parasite and host genome copy number in a sample provides a simple and reliable method of assessing T. parva load in infected bovine lymphocytes, and is accurate over a wide range of host-to-parasite DNA ratios. Knowledge of the proportion of target DNA in a sample, as enabled by this method, is essential for efficient high-throughput genome sequencing applications for a variety of intracellular pathogens. This assay will also be very useful in future studies of interactions of distinct host-T. parva stocks and to fully characterize the dynamics of ECF infection in the field
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